This invention relates to fuel supply system for an auxiliary motor vehicle heating device (which operates independently of the vehicle engine and can be used to preheat the vehicle or engine before occupancy, or to warm a sleeping compartment while the vehicle is at rest and the engine turned off), having a fuel storage reservoir which can be filled from the fuel supply for the vehicle's internal combustion engine; More particularly, a fuel supply system wherein a fuel pump is provided for supplying fuel to the heating device from the fuel storage reservoir.
A fuel supply device of the initially mentioned kind is described in German Offenlegungsschrift No. 23 27 830, wherein an intermediate reservoir is disposed as a fuel storage reservoir in the return line leading away from the internal combustion engine toward the motor vehicle fuel tank. The overflow side of the intermediate reservoir is connected with the fuel tank of the motor vehicle, and furthermore, a ventilation line is provided at the intermediate reservoir which permits ventilation and overflow drainage via the tank of the motor vehicle. In this arrangement, the fuel flows continuously from the return side of the combustion engine through the intermediate reservoir and passes back to the fuel tank via the return line once the intermediate reservoir has been filled to capacity. A metering nozzle, serving as a fuel supply device to the heating unit, is connected with the outlet line of the intermediate reservoir.
The cost of installing fuel supply device for an auxiliary vehicle heater is very high since several lines and line branches have to be provided at the point of separation to the fuel supply unit of the internal combustion engine. Furthermore, depending upon the vehicle fuel tank design, ventilation and overflow drainage of the intermediate reservoir can lead to problems, particularly when the engine is standing still.
Accordingly, it is a primary objective of the invention to provide a fuel supply system for an auxiliary fuel heating device which overcomes the difficulties described above by permitting a reliable and largely degassed fuel supply to the auxiliary vehicle heating device from the fuel supply equipment for the vehicle engine, and which, in a simplified manner, can be installed into the vehicle with a minimum of installation time.
In accordance with the invention, a fuel supply device for an auxiliary vehicle heating system is characterized in that the fuel storage reservoir is arranged in the engine compartment of the vehicle, and is filled with fuel in a batchwise manner from any desirable fuel supply unit of the internal combustion engine, and in that a ventilating valve, leading to the environment, is provided at the fuel storage reservoir.
In the fuel supply system of the present invention, the fuel storage reservoir has a separate ventilating device, formed by a valve, so that the supply of fuel to the auxiliary vehicle heating device from the fuel storage reservoir is independent of, respectively, a connection with, or a corresponding ventilation by the fuel tank of the vehicle. Accordingly, the respective design of the motor vehicle's tank does not have to be a consideration for the installation of the inventive fuel supply device. Even if gas bubbles should form in the fuel supply device of the internal combustion engine, they will not have an adverse effect on the fuel supply of the heating device inasmuch as the fuel supply reservoir in the inventive device simultaneously serves as a separator for gas bubbles.
Advantageously, a fuel pump is arranged in the fuel supply device and is surrounded by the fuel in the fuel storage device so that the pump is constantly cooled by the fuel and consequently can reliably supply fuel to the heating device. As the fuel storage reservoir already contains filtered fuel, and the fuel pump is arranged in the fuel storage reservoir, it is also very effectively protected against contamination.
In order to permit a filling of the fuel storage reservoir, a line having a longitudinal slot-like passage to the interior of the fuel storage reservoir can be provided at the outside of the reservoir and at the height of the reservoir fill level, thereby enabling flow in the line to bypass the reservoir when it is full. In order to have the widest choice regarding the installation of the fuel supply reservoir, positioning of the fuel pump relative to the fuel supply device is appropriately coordinated.
In accordance with a further aspect of the invention, the intake for the fuel pump is designed to be incorporated within the fuel storage reservoir so that the pump and reservoir can be handled as a single unit that can be inserted at the fuel consumption point of the fuel supply device of the vehicle's internal combustion engine and can be connected with the auxiliary motor vehicle heating device.
In order to ensure a space-saving design of the fuel supply reservoir, for installation purposes, its outer dimensions are adapted to the contour of the vehicle heating device.
A drainage unit can be provided in the fuel storage reservoir to reduce the danger of the fuel pump freezing at very low temperatures. Alternatively, or additionally, a fuel heating device can be provided in the fuel storage reservoir, whereby a gelatinizing of the fuel in the fuel storage reservoir is avoided, and when using diesel fuel, it is heated to achieve sufficient pumpability.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention.